NASA Composite Crew Module (CCM)

HyperSizer was used by the NASA team to perform structural analysis and margins of safety predictions for the testing of the Composite Crew Module. HyperSizer software was used throughout the almost three-year project to optimize the design, weight, and manufacturability of the CCM, which is constructed of honeycomb sandwich and solid laminate composites. HyperSizer predictions matched all test measurements performed by NASA.

"I’ve been working with composites for 25 years and the CCM is the most complicated structure I’ve ever dealt with," said Jim Jeans, chief architect for NASA on the project. "The fact that it passed these tests with flying colors is a credit to HyperSizer, which we used in every phase of the project. The sizing and strain predictions all held up as the software predicted."

Full scale static test of the NASA Composite Crew Module was performed at Langley Research Center. HyperSizer was used by NASA team to perform structural analysis and margins of safety predictions for test.

“Since the structure is designed to minimum margins in many areas, the ultimate test exercised the structure close to the minimum material properties and I assure you there was celebration amongst the team when we achieved that critical milestone!” Mike Kirsch, CCM Project Manager

This was a milestone achievement for HyperSizer software, the NASA Composite Crew Module design team, and the nation’s plans for future use of composites in space vehicles. HyperSizer was used as a primary tool by NASA to design and analyze the composite variant of the metallic Orion crew module which houses the astronauts throughout the flight mission from launch to ocean splashdown. The CCM constructed of honeycomb sandwich panels and solid laminates is weight optimized to over fifty loading scenarios. Three of these loadings were selected for test validation: internal pressurization, parachute pull, and abort launch system thrust force. In every load case tested, HyperSizer accurately predicted the structural response strain gage readings of the composite material under loading, and more importantly, achieved the required loading without structural failure.

Partners: Led by the NASA Engineering and Safety Center (NESC), the project team was a partnership between NASA and industry, including design, manufacturing, and tooling expertise. Partners were civil servants from nine NASA Centers - ARC, DFRC, GRC, GSFC, JSC, JPL, KSC, LaRC, and MSFC; the Air Force Research Laboratories; and contractors from Alcore, ATK, Bally Ribbon Mills, Collier Research Corporation (HyperSizer), Genesis Engineering, Janicki Industries, Lockheed Martin, and Northrop Grumman. The CCM team operated in a virtual environment, electronically connecting participants across the country.

NASA Ares I Exploration Vehicle Composite Crew Module

Fig.1, Ares I Crew Launch Vehicle that launches the NASA Crew Module

The Project

The NASA NESC Composite Crew Module (CCM) team was chartered to develop a Crew Module (CM) design tailored to composites and to characterize the design drivers such as geometry, mass, manufacturability, inspectability, repairability, damage tolerance, crashworthiness, micro-meteoroid and orbital debris, and radiation shielding. The CCM team constrained their scope to retain the reference design outer mold line, maintain the inner mold line within 1.5 inch of the reference design, and to maintain the interface points at the Launch Abort System and the Service Module. This was a parallel effort to the NASA and Lockheed Martin metallic crew module (CM) referred to as Orion (launched and interfaced with other hardware modules) pictured in Fig. 2. The composite crew module (CCM) was designed to the same loading environment as the metallic crew module. A primary intent by NASA was to gain experience designing, analyzing, and testing flight weight composite structures for potential future space missions [1,2,3,4].

Fig. 2, Left - the metallic crew module with the aeroshell and heatshield shown. Right - a cutaway view of the metallic pressure shell and heat shield carrier panel.

This team developed three concepts: geometrically stiffened laminate, stiffened sandwich (utilizing the aluminum-lithium aeroshell) and monocoque design analysis and sizing iterations, but none were optimized with respect to mass or manufacturability. Each concept had a different level of design maturity, and all three had less definition than the reference Crew Exploration Vehicle Project aluminum-lithium design. Comparing estimated mass values at this stage, yield rough order of magnitude values at best. The design did not include analysis of landing or dynamic loads, reusability, thermal loads, subsystem packaging and integration, or development costs and schedule implications of incorporating a composite solution.

Fig. 3, The Composite Crew Module project is an alternate design of the pressure shell and maintains the essential design intent and interfaces of the baseline crew module illustrated in Fig. 2. The figure insert in red shows how the pressure shell fits into the existing aeroshell.

Design Engineering

Fig. 4, CCM preferred sandwich closeout design.

The analysis methods were performed with HyperSizer® software. This tool resulted in significant design-cycle time reduction from software integration and analysis automation that resulted in the ability to analyze a large number of design configurations of the CCM. There were several benefits of HyperSizer integration on the CCM design and analysis process, along with risk reduction from the use of final analysis methods earlier in the design process.

This project, like any other aerospace design, made use of composite material’s strength and weight efficiency, and flexibility of fabrication. To gain the most benefit with composites, engineers perform many trade studies to explore the design space and find an optimum set of panel concepts, dimensions, and layup stacking arrangements, referred to as sizing optimization. The need in their set of analysis tools is to evaluate many design alternatives very rapidly and with enough analysis fidelity to discern true differences in performance in competing vehicle configurations and design features.

Software for Composite Design and Analysis

To accomplish this level of composite-specific analysis automation, NASA used a two-part combination of software tools. The first software is FEA. The FEA packages used on this project were NEi Nastran, NX/Nastran, MSC/Nastran, and Abaqus. The other type of software, HyperSizer®, was used to perform most of the composite analysis and sizing optimization.

HyperSizer incorporates almost all composite analyses required for aerospace structures in a comprehensive user interface that couple very tightly with the individual analyses and their corresponding margins of safety stress reporting. Starting with importing FEA-computed internal element unit forces from the global finite element model of the vehicle’s panels and beams, HyperSizer solves for hundreds of different failure modes very rapidly using material allowables and its failure criteria that are specifically correlated to test results. Its rapid analyses allows full vehicle models to be analyzed to hundreds of load cases while also including stress/strain gradients from local detail effects.

Final Analysis

Fig. 7, Each color is either a unique solid laminate layup or sandwich design.

Those unplanned that become known later: fabric ply overlap regions, fiber angle alignment

The following failure analyses for the design of the full scale NASA Composite Crew Module (CCM) were provided by the HyperSizer software with automated preliminary design sizing and final margin-of-safety stress reporting:

Composite material strength

Sandwich specific analyses

Ply drop-off transitions

Bonded joints

Bolted joints

Conclusion

Having the same high fidelity analyses available during preliminary design, as used in final design, is very valuable in producing hardware concepts that have less weight growth and required strength and stability during final design. By including these analyses early in the design cycle, weight growth is minimal, and weight savings can be obtained by finding appropriate alternate designs.

The CCM team recommended that NASA continue the composite CM structural design and include fabrication manufacturing and tooling expertise in a collaborated environment. The figures below are photographs of the CCM during full-scale fabrication.